In a conventional seat heater, a planar heater includes an electric heating wire disposed on a base material over an entire surface thereof so as to wind therethrough at predetermined intervals. The planar heater is interposed between a skin and a main pad of both a seat cushion and a seat back of the seat. When the electric heating wire is energized, the heater generates heat to make a seat occupant warm and comfortable even in a cold season (see, for example, Patent Document 1).
Another seat heater has been proposed having a plurality of separated heating elements embedded in the seat. The heating elements are selectively energized to generate heat depending on seat-occupant's symptoms to be ameliorated. This heater is used to locally heat seat-occupant's sites associated with the symptoms to ameliorate them (see, for example, Patent Document 2).    Patent Document 1: Japanese Laid-Open Patent Publication No. 2-129886    Patent Document 2: Japanese Laid-Open Patent Publication No. 2007-283932